1. Field of the Invention
The invention relates to an automatically compensatable device for measuring a pressure difference.
Such devices are advantageously used for detecting the through-flow of a flow medium, wherein the detected through-flow serves for example for regulating the feed flow of fresh air to a room or for power accounting purposes.
2. Description of the Prior Art
Devices of that kind can advantageously be used in a system with a variable volume flow, in which the zone temperature is regulated by varying the air volume flow. This process which is known by the term VAV (variable air volume) is generally used for cooling purposes when the feed air temperature is lower than the desired temperature.
The use of such devices however is not limited to the heating, ventilation and air-conditioning art. Depending on the respective configuration of the device involved, it is possible to detect differential pressures in gaseous or liquid flow media.
A device of this kind is known (WO 90/05289 A1) which includes a differential pressure sensor, a valve and a circuit having a plurality of operational amplifiers. That device is so designed that the differential pressure sensor can be short-circuited by the valve.
U.S. Pat. No. 3,509,767 also discloses a device in which a differential pressure across an aperture can be detected by a differential pressure sensor. The device has a plurality of valves which are actuable in such a way that the differential pressure sensor can be short-circuited in relation to a differential pressure applied thereto.
Known devices of that kind are relatively loud and have a plurality of components such as a sensor, a valve, a valve actuating assembly, an electronic system and connecting elements which have to be installed on site at a measurement location. The known devices therefore require at the location of installation a relatively high level of fitment expenditure and installation space and they are also relatively costly and susceptible to trouble.